bazel: correctly stamp `build.channel`, `log.crashReportEnv`

#67278 took care of #66853, but that still leaves a couple variables:

```
# TODO(ricky): Also provide a way to stamp the following variables:
# - github.com/cockroachdb/cockroach/pkg/build.channel
# - github.com/cockroachdb/cockroach/pkg/util/log.crashReportEnv
```

Epic CRDB-8351

Jira issue: CRDB-8467